1. Field of the Invention
This disclosure relates to sensors for determining an absolute angle of rotational objects in a prosthetic joint.
2. Description of the Related Art
Modern, computer controlled prosthetic devices have many advantages over conventional prosthetic devices. For example, computer controlled prosthetic devices can allow the amputees to walk with limited fear of stumbling or falling, allow amputees to lead a more active lifestyle, and improve the likelihood that amputees can realize their full economic potential. This is especially beneficial for the thousands of new amputees each year and the millions of existing amputees.
However, modern, computer controlled prosthetic devices are limited in some aspects due to the number of electrical parts. These limitations can include, for example, the shortened lifespan of its electrical parts, such as a sensor to measure an angle of a prosthetic joint, due to dust, moisture, or other environmental elements. The dust, moisture, and other environmental elements can also limit, for example, the type of activities that an amputee can perform while using the modern, computer controlled prosthetic devices. However, computer control of a joint during normal ambulation, or gait, requires robust and accurate sensors to provide input to the control strategy. These sensors could detect information such as joint position, knee angle, forces, weight bearing forces, ankle torque, knee torque, velocity, or acceleration.
Other limitations with the sheer number of electrical parts include the power draw. Naturally, increasing the number of electrical parts correspondingly increases the power required to operate the prosthetic device. One method to support this large increase in power draw is to increase the battery size. However, increasing the battery size increases the size and weight of the prosthetic device. This is undesirable since the prosthetic device should be the same length as the intact limb of the amputee. Thus, larger prosthetic devices may be undesirable for amputees that are shorter in height, especially children. Furthermore, the added weight can hinder the movements of the amputee, regardless of height. However, children may be especially impacted as they will not be as muscularly developed and may not be adept at handling the extra weight of the larger battery. Thus, any decrease in power consumption is beneficial to amputees because of the corresponding reduction in the size and weight of the prosthetic device.
Thus, there is a need for a sensor device for determining an absolute angle of a prosthetic joint, and which is resistant to environmental elements and has a reduced power draw.